4.4 - Managing Electrostatic Discharge

Overview of Static Electricity

  • Definition of static electricity: A buildup of electric charge on an object's surface.

  • Common experience: Feeling a spark when touching a metal doorknob after walking on a carpet.

Understanding Electrical Potential

  • Explanation of electrical potential:

    • The difference in electric charge between two objects (e.g., a person and a doorknob).

    • The spark occurs when the potential between the two is equalized.

  • Static electricity is non-harmful until discharged.

Impact on Computer Components

  • Sensitivity of computer components to electrostatic discharge (ESD):

    • Silicon, commonly used in computers, is highly susceptible to ESD.

    • Example of damage caused by ESD captured by a scanning electron microscope at 4,300 magnification.

  • Measurement of discharge:

    • Typical discharge when touching a doorknob: approximately 3,500 volts.

    • Voltage threshold for damaging computer equipment: 100 volts or less.

Minimizing Electrostatic Discharge (ESD)

  • Environmental conditions to reduce ESD:

    • Maintaining humidity over 60% can help prevent discharges; however, this may be uncomfortable.

  • Best practices for preventing ESD when working with computers:

    1. Self-grounding technique:

    • Touch a metal part of the system's chassis to equalize electrical potential between the person and the equipment.

    1. Unplugging power connections:

    • Ensures no electrical shock can occur and does not affect ESD prevention.

    1. Avoiding connections to building's electrical ground:

    • Electrical ground can become energized, posing risks.

Use of Anti-Static Equipment

  • Wearing anti-static straps:

    • Strap is connected to a wrist and other end to metal part of the device being worked on.

  • Use of anti-static pads:

    • Positioned on the work surface to ensure consistent grounding.

  • Anti-static mats:

    • Placed on the floor to minimize ESD while working.

    • Connection required to a grounded surface or to the device.

  • Anti-static bags for transport:

    • Specially designed to hold components securely, minimizing the risk of static damage.

Technician Practices

  • Image of a technician using an anti-static pad and strap:

    • Ensures proper grounding and protection from ESD while working on devices.

  • Anti-static strap features:

    • Includes a breakaway snap for safety, allowing easy disconnection when moving away.

    • Reconnection is simple upon return to the work area.

Component Handling and Storage Recommendations

  • Avoid handling components directly to minimize ESD risk:

    • Handle by the edges rather than touching electrical contacts.

  • Ideal storage environment for components:

    • Temperature range: 50 to 80 degrees Fahrenheit (10 to 27 degrees Celsius).

    • Maintain low humidity levels to protect sensitive electronics.

  • Use of silica gel packs:

    • Effective at controlling humidity when stored in anti-static bags.

  • Proper storage containers:

    • Original packaging is ideal; if unavailable, using bubble wrap with anti-static bags is a practical alternative.