Cleanroom Gloves - Balancing ESD and Cleanliness

[dropcap]C[/dropcap]leanroom environments in the electronics, nanotechnology and semiconductor industries are especially sensitive to static. For this reason, the electrostatic discharge (ESD) property of cleanroom gloves worn by workers is an important consideration.

Electrostatic discharge damages the electrical characteristics of a semiconductor device. It can also cause equipment to malfunction or fail, interfering with the normal operation of an electronic system.

An electrostatically charged surface can also attract and hold onto contaminants – bad news for the cleanroom environment. Airborne particles can cause defects in a device’s electrical circuitry.

Controlling ESD

Failing to control ESD in a cleanroom can be expensive. Static electricity damages electronics, leading to increased manufacturing costs and lower production yields, negatively affecting a company’s reputation and profitability. One way that cleanrooms manage static charge is by using static dissipative materials.

Static dissipative materials fall somewhere between insulative and conductive materials. There is electron flow through or over the material, but in a controlled fashion, by the surface resistance or volume resistance of the material. It allows the charge to dissipate, or transfer slowly to ground without causing damage.

Cleanroom Nitrile Gloves Preferred

When selecting gloves for cleanroom applications where static discharge could harm the product, or where static could lead to contamination, nitrile gloves are the preferred choice.

Gloves made from natural rubber latex are inherently static insulative, holding on to a charge and releasing it in an uncontrolled manner, leading to damage. The surface resistance of nitrile gloves, however, is normally on the border of insulative and static dissipative. To be considered static dissipative, the glove should have a surface resistance of more than 1 x 10⁵ but less than 1 x 10¹¹ ohms/sq. The surface resistance test results for a glove can usually be found on the manufacturer’s product information sheet.

Balancing ESD with Cleanliness

Interestingly, the cleaner the glove, the lower the glove’s ESD protection. Tom Lesniewski and Kenn Yates of the TRW Space and Electronics Group conducted an evaluation of the cleanliness and ESD protective properties of cleanroom materials, including 7 different types of nitrile gloves.

They found a clear trend – as non-volatile residue (NVR) increased, surface resistance decreased. The surface contaminants on a glove make the glove more static dissipative, especially in higher humidity.

Because there is clear tradeoff between cleanliness and charge dissipation rate, cleanrooms requiring a high level of ESD protection should choose a cleanroom glove only as clean as it needs to be for the ISO level of the cleanroom.

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HandPRO Cleanroom Nitrile Gloves provide the moderate static dissipation needed to protect highly ESD sensitive devices from damage. The gloves are also very clean, making them a contamination-free solution for cleanrooms requiring low ionic contamination.