Just 20 years ago, you cold find little in the way of electrostatic discharge (ESD) control products and services, let alone standards for care. But today the yearly costs of damaged electronic devices are measured in the billions of dollars and manufacturers now follow well defined best practices for static control. Intimidated by the ESD market? Don’t be! As a packaging distributor, an important element of their total solution in is your hands.
Electrostatic buildup and discharge is an old problem that’s found a new target in circuitry. Hundreds of years ago, military forts used static control procedures to keep electrostatic discharge from igniting powder stores. By the time of the U.S. Civil War, paper mills throughout the country fought electrostatic buildup with grounding wires and steam drums. Today you’ll find customers for electrostatic control products throughout the electronics industry, in clean room applications and in printing and graphic arts.
ESD packaging provides a significant opportunity for packaging distributors. It is business that’s bigger, less price sensitive and more sustainable than many packaging categories. Good products and subject matter expertise brings real value to the ESD packaging consumer. And it’s easier to master the subject than you might think.
Anyone who has walked on a carpet in socks and reached to turn on their Christmas tree lights, combed their children’s hair in January or rubbed balloons on their heads has experienced static electricity first hand. Here are two things you should know about the formation of static charges:
Electrostatic charges are created by the contact and separation of two dissimilar materials. It’s called triboelectric charging and it involves the transfer of electrons from one surface to another. Triboelectric charging worsens when you have:
- Insulating Materials. As with rubber balloons, considerable charges build up on insulators.
- Greater Surface Area. Like carpet pile, greater surface area offers more surface contact for triboelectric charging.
- Lower Relative Humidity. Like the winter months, any situation with low humidity promotes charge buildup. At 90% relative humidity, activities produce aout 1/30th of the static electricity generated at 20% relative humidity.
Once statically charged, materials also have electrostatic fields associated with them. Think of someone’s hair standing straight up in the winter. A conductive object, like a circuit board, brought near an electrostatic field can be polarized by something called induction.
COPING WITH STATIC
At levels well below what you can feel, electrostatic discharge can destroy circuitry. Like very high volumes of water rushing through narrow systems of pipes, surges in voltage create currents that today’s micro-circuitry can’t handle. They may fail immediately (a catastrophic failure) or weaken and fail later (a latest defect). Latent defects are more costly by far, resulting in user failures, field repairs, downtime and lowered customer satisfaction.
You should know that damage from ESD happens from one of three events:
- Static discharge to an electrical device
- Static discharge from an electrical device
- Static discharge induced on an electrical device by a static field
In Fundamentals of ESD Control, the ESD association describes a number of steps of minimize damage from ESD. These steps include developing products to be as ESD insensitive as possible, identifying electrostatic protected areas and defining control levels. They then speak to reducing charge generation and dissipating charges with ESD controlling footwear, workstations, grounding straps and wrist straps. Finally, they refer to ESD protective packaging for handling and transport. That’s where we come in. Let’s take a look at two of the more common film categories for managing ESD.
STATIC DISSIPATIVE BAGS
Static dissipative bags, often called “pink poly” or Pink Anti-Static “PAS” for their traditional color, have provided protection against static discharge for many years. An economical option, these bags are most often selected for non-critical applications where shielding against static fields is not important.
Typically made of low density polyethylene, they work by employing the use of a humectant additive to pull moisture from the air. With a microscopic layer of water molecules at the film surface, it becomes far more difficult to generate a charge. Charges that are generated dissipate quickly before they can accumulate to hazardous levels.
Amines – the first widely used anti-static additive – are very effective humectants, but they can be corrosive to other plastics like polycarbonate. So in recent years, they have been replaced with amides. Similar in chemistry, these amine-free films contain higher levels but achieve the same static dissipative performance.
To protect contents from electrostatic fields (triboelectric charging) customers turn to Static Shielding bags. Sometimes called Transparent Metallic Shielding bags for their silvery see-through nature, they contain a complex arrangement of layers.
- A static dissipative later provides an outer-surface that is low charging.
- A metal-containing layer provides a conductive inner layer that suppresses electric fields.
- A polyester layer provides added tear and puncture strength.
There are two common types of shielding bags – Metal In and Metal Out. With Metal In bags, the conductive later is buried. These are more durable, less expensive and more commonly used than Metal Out bags. But when customers are looking for still more rapid charge dissipation, Metal Out bags benefit frmo placing the metal layer nearer the surface. Starting at about twice the cost of traditional pink anti-static bags, static shielding bags are usually provided in recloseable, layflat configurations.
ESD PACKAGING IN YOUR MARKETPLACE
In computers, telecommunications devices, electronic games and toys, pathways on integrated circuits are getting smaller, faster and more vulnerable to ESD. Yet the technology of ESD packaging remains fairly straightforward. Distributor sales reps who take time to learn about ESD packaging tell us that static dissipative products provide terrific opportunities to shine.
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