By Phil E. Tuma, 3M Electronics Markets Materials Div., and Scott Knoll, Lydall Industrial Thermal Solutions

Many recirculating chiller applications require electrically nonconductive or “dielectric” heat transfer fluids. A dielectric fluid may be required to maintain electrical isolation of components maintained at an electrical potential or may be desirable from a reliability viewpoint to prevent component damage in the event of a fluid leak.

Although there are many dielectric fluids available, many are not suitable for use in semiconductor manufacturing. For example, petroleum-based fluids, hydrocarbons, or silicone oils tend to be flammable or combustible. Others are eliminated for thermal stability reasons or because they leave behind residue and odor after a spill. Chlorinated fluids are discounted because they are ozone depleting or highly regulated for their toxicity [1].

The choices remaining are deionized (DI) fluids and fluorinated fluids. DI fluids — including water and/or ethylene or propylene glycol — may also contain corrosion inhibitors. Referred to as “DI/glycol fluids,” they are still used quite often in etch, chemical vapor deposition (CVD), and even some automatic test (ATE) applications. However, they were most common prior to the early 1990s.

At that time, evolving process temperatures necessitated use of fluorinated fluids, which include perfluorocarbon (PFC) fluids [2] and hydrofluoroether (HFE) fluids [3]. Today, both DI/glycol and fluorinated fluids are used. This paper discusses the inherent advantages and disadvantages of each category. As will be shown, fluorinated fluids, when used in a properly designed system, are more versatile, more economical, more reliable, and easier to use than DI/glycol fluids.

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Julie MacShane, Managing Editor, email: [email protected].