ESD Control Measures in the Cleanroom
Static control products are used throughout the electronics, defense, fiber optics, telecommunications, medical, disk drive, and automotive industries for the protection of sensitive electronic components inside as well as outside of the electrostatic discharge protective area (EPA). ESD (Electrostatic Discharge) engineers or site coordinators, packaging engineers, quality assurance, manufacturing engineers, marketing and procurement groups need to select products based upon a formalized “Materials Qualification Process” (MQP) to verify a supplier’s technical datasheets or specifications.

The U.S. Military was instrumental in requiring adherence to Mil Std. 263 that features test methods for the qualification of materials. In addition, the EIA (Electronic Industry Alliance) developed procedures for materials selection. Today, the ESD Association leads the effort with ANSI/ESD S20.20-1999, followed by ANSI/ESD S541-2003 (ESD Packaging and Materials Standard). Moreover, this document serves as an invaluable reference standard and roadmap in the evaluationof packaging and materials.

Qualifying ESD products on the word of suppliers or specification sheets without in-house or third party testing can be sacrificing adherence to ESD protocols. The practice of “grandfathering” or accepting products based upon the performance of a previous design is circumventing “due diligence” and short circuiting quality assurance. If one does not actually measure to secure real data, then an organization is opening the door for corrective actionsand product failures.

This article discusses ESD standards and industry evaluation practices for measuring the effectiveness of selected products used to protect electrostatic sensitive devices from ESD related hazards. The following products were tested to illustrate procedures used in evaluating materials:

1. Static Shielding & Moisture Barrier Bags
2. ESD Gloves
3. ICP Vacuum Formed Trays

Other considerations such as chemical or mechanical characteristics will not be discussed due to limited article space.

Testing Procedures
Table 1 summarizes the evaluation procedures which were used to examine thevarious material types.

ESD Standards: [1]
ANSI/ESD S541-2003: Packaging Materials for ESD Sensitive Items
This standard describes the packaging material properties needed to protectelectrostatic discharge (ESD) sensitive electronic items and references the testingmethods for evaluating packaging and packaging materials for those properties.

ANSI/ESD S8.1-2001: Symbols–ESD Awareness
Three types of ESD awareness symbols are established by this document. The first type is to be used on a device or assembly to indicate that it is susceptible to electrostatic charge. The second type is to be used on items and materials intended to provide electrostatic protection. The third type indicates thecommon point ground.

ANSI/ESD STM11.11-2001:
Surface Resistance Measurement of Static Dissipative Planar Materials
This standard defines a direct current test method for measuring electrical resistance, replacing ASTM D257-78. Designed specifically for static dissipative planar materials, this standard is used in packaging of ESD sensitive devices and components.

ANSI/ESD STM11.12-2000:
Volume Resistance Measurement of Static Dissipative Planar Materials
This standard provides test methods for measuring the volume resistance of static dissipative planar materials used in the packaging of ESD sensitive devices and components.

ANSI/ESD STM11.13-2004: Two-Point Resistance Measurement
This standard test method measures the resistance between two points on a material’s surface. This test method was established for measuring materials where the geometry of a concentric ring electrode is to large or inappropriate for conductingsurface resistance measurements per ANSI/ ESD STM11.11-2001.