Blog Archives

Storage and Transport of ESD Sensitive Items

Follow us on Twitter  View our profile on LinkedIn  YouTube  GooglePlus

We thought today we could focus on ESD during storage and transport. If you have read our recent post on Tips to Fight ESD, you will remember how important it is to protect your ESD sensitive items when leaving an EPA. Yet, too often we see customers who have the perfect EPA, but when it comes to transporting and storing their precious components, it’s all falling apart.

1. Packaging required for transporting and storing ESD sensitive items

During storage and transportation outside of an EPA, we recommend that ESD sensitive components and assemblies are enclosed in packaging that possesses the ESD control property of shielding.

Remember:

  • In ‘shielding’ we utilise the fact that electrostatic charges and discharges take the path of least resistance.
  • The charge will be either positive or negative; otherwise the charge will balance out and there will be no charge.
  • Charges repel so electrostatic charges will reside on the outer surface.


2. The Faraday Cage effect

A Faraday Cage effect can protect ESD sensitive items in a shielding bag or other container with a shielding layer. To complete the enclosure, make sure to place lids on boxes or containers and close shielding bags.

ESDPackaging
Cover must be in place to create Faraday Cage and shield contents.

3. Types of shielding packaging

The below list gives a few examples of what types of shielding packaging is available on the market. This list is by no means complete; there are many different options out there – just make sure the specifications state “shielding” properties.

  • Metal-In Shielding Bags
    ESD bags which protect ESD sensitive items. The ESD shielding limits energy penetration from electrostatic charges and discharge. They offer good see-through clarity. Available with and without dissipative zipper.
  • Metal-Out Shielding Bags
    Integral antistatic and low tribocharging bags which will not electrostatically charge contents during movement. Bags have an aluminium metal outer layer of laminated film. Available with and without dissipative zipper.
  • Moisture Barrier Bags
    Offer ESD and moisture protection and can be used to pack SMD reels or trays. Check out this post for more information on MBB and ESD Control.
  • Bubble Shielding Bags
    These bags combine the “Faraday Cage” and mechanical protection. They shield about twice as well as normal shielding bags of equivalent size.
  • Component/Circuit Boards Shippers
    These boxes offer an efficient way of shipping or storing ESD sensitive circuit boards and other items. They provide ESD shielding with the lid closed. The foam cushioning reduces stress from physical shock.
  • In-Plant Handlers/Storage Containers
    Shield ESD sensitive items from charge and electrostatic discharges (with lid in place). They provide ESD and physical protection for ESD sensitive circuit boards.


4. Additional options for storing ESD sensitive items

Do you have the following in place?

  • ESD flooring
  • Grounded personnel (using foot grounders). Read this post for more information on how to ground moving personnel.
  • Grounded racking

TEAMOperator wearing foot grounders

IF (and this is a BIIIG IF) the above requirements are fulfilled, you can use conductive bags or containers to store your ESD sensitive items. Conductive materials have a low electrical resistance so electrons flow easily across the surface. Charges will go to ground if bags or containers are handled by a grounded operator or are stored on a grounded surface.
Conductive materials come in many different shapes and forms:

  • Conductive Black Bags
    Tough and puncture resistant bags which are made of linear polyethylene with carbon added. The bags are heat sealable.
  • Rigid Conductive Boxes
    Provide good ESD and mechanical protection. Boxes are supplied with or without high density foam for insertion of component leads or low density foam which acts as a cushioning material.
  • PCB Containers
    Are flat based and can be stacked. They are made of injection moulded conductive polypropylene.

Again, there are many more options available on the market so make sure you do your research.

Note: we do not recommend using conductive packaging to transport ESD sensitive devices. Also, pink antistatic and pink antistatic bubble bags are not suited for storing or transporting ESD sensitive components.

5. Final thoughts

Packaging with holes, tears or gaps should not be used as the contents may be able to extend outside the enclosure and lose their shielding as well as mechanical protection.
Also, do not staple ESD bags shut. The metal staple provides a conductive path from the outside of the ESD bag to the inside. The use of a metal staple would undermine the effectiveness of the ESD bag making a conductive path for charges outside the bag to charge or discharge to ESD sensitive components inside the bag. To close an ESD bag, it is recommended to heat seal or use ESD tape or labels after the opening of the bag has been folded over. Alternatively, you can use ESD bags with a zipper.

Picture5Sealing ESD Bags the correct way

One final word of warning:
When ESD sensitive items are unpackaged from shielding bags or other containers, they should be handled by a grounded operator at an ESD workstation

 

 

ESD Control, Return on Investment

Ryne C. Allen

Desco Industries Inc. (DII), Employee Owned

November 1999

Reproduced with Permission, EE-Evaluation Engineering, November, 1999

INTRODUCTION

I. Introduction to ESD Control Programs

ESD Control programs are an essential part of a quality process and are always needed when handling ESD sensitive electronic/semiconductor devices. The extent of the ESD Control program is determined by the ESD Sensitive (ESDS) devices themselves and how they are handled. Refer to article “How to Set Up an ESD Control Program” [1] for additional information.

One of the main reasons that companies deploy ESD Control programs is to save money. Increased throughput and decreased scrap can yield a Return On Investment (ROI ) of up to 1,000% per [2]. A secondary reason is to comply with their customers’ and ISO 9000 type programs’ requirements. Whatever reason, setting up and implementing an ESD Control program will almost always produce favorable financial results.

II. Cost Reduction via ESD Control Programs

Having ESD awareness and following through with an ESD Control program is essential in reducing quality failures due to ESD. ESD can affect product reliability with catastrophic damage which is readily apparent to latent degradation. Latent degradation is particularly expensive requiring costly inspection and rework cycles in-house or product failure in the field. Maintaining good ESD controls will improve product throughput or yield, increasing reliability in the field which improves customer satisfaction leading to increased future business.

One test equipment manufacturer noted that GMR heads were being damaged during or after testing. These heads are extremely sensitive to ESD, and require additional handling precautions.

It is very important when designing and implementing an ESD Control program to know the ESD susceptibility of the ESD Sensitive (ESDS) devices you are trying to protect. Classification of these devices should include all simulation models human body model (HBM), Machine Mode (MM), and Charged-device Model (CDM) that will properly characterize the devices’ sensitivity when handled at various locations within the facility [6]. This will allow for the most economical program design.

Gene Chase, an ESD Consultant with ETS Inc., is quoted as saying “Millions of dollars are lost every year due to ESD [4]. Many of these incidents occur within the computer and communications industry.” Examples of losses from ESD may be any of the following:

  • Lost Time
  • Loss of Connection
  • Loss of Data
  • Shocks to Personnel
  • Upset to A System Requiring A Re-Boot
  • Damage to Equipment
  • Equipment Hardware Failure

To properly determine the return on investment (ROI) from your ESD Control program, you must collect return, repair and scrap cost data before and after implementation.

To continue reading ESD Control, Return on Investment Click Here.

%d bloggers like this: