Friday, May 27, 2011

Elements of an Effective ESD Control Program – Part 1

Written and researched by Eric Puszczewicz, Marketing Manager, Transforming Technologies

Electrostatic Discharge (ESD) has been a threat for centuries, dating as far back as the 1400s when European and Caribbean forts were using static-control procedures and devices to prevent electrostatic discharge ignition of black powder stores. ESD, simply put, is the sudden transfer of an electric charge from one conductive surface to another. A common example of ESD is the annoying shock one receives when touching a doorknob after walking across a carpeted room.

In today's manufacturing environments, the threat from ESD is constant. As electronics become smaller and more sensitive, ESD can affect production yields, product reliability, and profits. The human body can feel ESD at 2,000 volts, but sensitive components can be damaged at as little as 15 to 30 volts (the image to the left shows a magnified example of ESD damage)! This is why ESD has sometimes been called the "invisible threat." To combat this potential threat, companies involved in electronics manufacturing today follow the industry accepted elements of an ESD Control Program.



An effective ESD Control Program requires three main parts:
  1. An ESD Prevention Program—This is developed by first assessing your ESD problem and then documenting the necessary equipment and procedures to follow to ensure electrostatic safe handling
  2. A Training Program—Required to ensure everyone is aware of, and understands, the ESD Control Program, use of equipment, and correct procedures
  3. An Audit Program—Required to ensure that equipment remains functional and that the ESD prevention procedures are correctly followed. There should be daily, monthly, and yearly checks
These three policies should be included in any effective ESD Control Program. In the next section, we’ll take a closer look at specific procedures and materials that become part of your program.

In the first section, we broadly touched on the three main parts of an ESD Control Program: ESD Prevention, Training, and Auditing. In this section, we'll look closer at each part—beginning with the ESD Prevention Program.

The ESD Prevention Program
Designing the ESD program should be made with company-wide input because ESD damage can occur at all stages in a product's life from fabricating to shipping. Appoint an ESD manager responsible for making sure that all aspects of the ESD program are carried out. ESD problems should be assessed through a facility audit and a close examination of production losses. This information will be critical when deciding what equipment and procedures to implement.

An Electrostatic Protected Area (EPA) area should be established where sensitive materials can be handled. An EPA is a prohibited region where items or activities able to cause ESD damage to sensitive devices are not allowed. This area should be designated with ESD signs or floor marking tape.

All conductors in the EPA should be grounded to a common point ground and all insulators should be removed if possible. Insulators, such as plastic or glass, are materials that prevent the flow or transfer of electricity and cannot be grounded. Charges can accumulate on insulators, which cause many problems. Air ionization can neutralize any charge that builds on insulators and other materials that cannot be grounded. Ionizers produce positively and negatively charged ions and flood a surface area with Ions. Ions are charged particles that are present in the air and, as opposites attract, charges will be neutralized over time.

Work surfaces and floors within the EPA should be covered with grounded ESD matting, such as two-layer rubber or vinyl. Operators in the EPA should be grounded at minimum with a wrist strap and coil cord set or heel grounders. ESD garments such as jackets or gloves may also be advisable. Shelving, storage containers, and even pens can generate static, and these items should either be grounded or made from an ESD-safe material.

Test equipment is also necessary in the EPA to ensure that all devices are in proper working order. This equipment may include a wrist strap/footwear tester, a constant monitor, or a charge plate monitor.

That wraps up the first part of our series on the Elements of an Effective ESD Control Program. Please check back with The Q Source Resource soon for Parts 2 and 3 where we’ll examine the details of the Training and Audit Programs.

Special thanks to our guest blogger, Eric Puszczewicz from Transforming Technologies’ Static Care blog.

No comments: