A discussion of the testing of cleanroom gloves for both surface and static resistance.

[Part I of this article appeared in the December 2005 issue of Controlled Environments.
The final Part III will be in the February 2006 issue.]
(See Sidebar “Terms and Definitions” for ANSI/ESD S541-2003 terminology used in this article.)

ESD Control Measures in the Cleanroom: Recap
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). The ESD Association has developed an invaluable reference standard and roadmap in the evaluation ofpackaging and materials.

This three-part 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 testedto illustrate procedures used in evaluating materials:

1. Static Shielding & Moisture Barrier Bags (Appeared in the December issue of Controlled Environments)
2. ESD Gloves and vacuum trays (Current article)
3. Static decay (To be published in the February issue of Controlled Environments)
 

Resistance of ESD Cleanroom Gloves
Both ANSI/ESD STM11.11-2001 (Surface Resistance) and ANSI/ESD STM11.12-2000 (Volume Resistance) were used to evaluate the cleanroom static control gloves. ESD gloves should provide a path to ground through an individual wearing a wriststrap,dual grounding snaps on garments or through static control footwear. In addition to measuring six specimens on an insulative substrate (Figure 7), it is important to measure the gloves for volume resistance per ANSI/ESD STM11.12-2000 on a conductive surface (Figure 8). Note: The glove in Figure 8 extends over theconductive plate on an insulative substrate so as not to influence readings.

Figure 8 illustrates one of the leads being connected to the stainless steel plate while the other lead is affixed to the concentric ring’s outer ring. The gloves performed to the manufacturer’s specifications for both surface and volume resistance (Tables 5 and 6). The volume resistance measurements per ANSI/ESD STM11.12- 2000 indicate that the gloves exhibit continuity toground.

2-Point Resistance
Until the ESD Association’s issuance of ANSI/ESD STM11.13- 2003, many organizations were using alligator clips and makeshift probes to measure materials of irregular construction. The 2-point measurement standard test method providesa useful tool for the evaluation of vacuum formed materials (Figure 10).